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I. Fejes, M. Janáky; Interocular Differences in the Pattern Electroretinogram and the Visual Evoked Potential. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5875.
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© ARVO (1962-2015); The Authors (2016-present)
Pattern electroretinography (PERG) and pattern visual evoked potential (VEP) are commonly used methods for the objective evaluation of the function of the inner retinal layers and the visual pathway. Previous studies did not focus on the interocular differences in the normal responses, however, they may be relevant in the evaluation of the severity of a monocular functional abnormality. The aim of the study was to determine the normal side differences of the PERG and the VEP parameters.
PERG and VEP were recorded according to the International Society for Clinical Electrophysiology of Vision standards. Subjects (n=31, age=18-39 years) with best corrected visual acuity of 1.0 and without any ophthalmological or systemic diseases were tested. For stimulation black and white checkerboard of 20’ checksize was reversed at a rate of 1.8 Hz. PERG was detected with DTL electrode during binocular stimulation. In case of the VEP monocular stimulation was used. The absolute value of the side differences was determined, and the higher and lower response amplitudes were compared with paired t-test and Mann-Whitney-test.
No significant differences were found between the responses of the right and the left eyes. However, when comparing the higher and lower response amplitudes, the differences proved to be significant. In case of the PERG N35P50 and P50N95 amplitudes and the P50N95/N35P50 ratio the following absolute differences (mean±SD) were observed: 2.16±1.76 µV, 2.82±2.44 µV and 0.104±0.09 µV, respectively. In case of the VEP N75P100 and the P100N135 amplitudes and the P100N135/N75P100 ratio we found the following absolute difference values: 1.62±1.32 µV, 2.49±2.3 µV and 0.178±0.1 µV, respectively.
Previous studies only focused on the reproducibility of the responses, but not on the side differences. Our results revealed a significant side difference of the PERG and the VEP. According to the big differences between the range of the higher and the lower amplitudes, without taking the side differences into account, misinterpretation may occur and abnormalities may be kept hidden.
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